Vibrating flowmeters, such as, for example, densitometers and Coriolis sensors, are used for measuring a characteristic of flowing substances. For example, a vibrating flowmeter may measure a density, mass flow rate, volume flow rate, totalized mass flow, temperature, or any other information with regards to a fluid. Vibrating flowmeters include one or more flow conduits, which may have a variety of shapes, such as, for example, straight, U-shaped, or irregular configurations. The one or more flow conduits have a set of natural vibration modes, including, for example, simple bending, torsional, radial, and coupled modes. The one or more flow conduits are vibrated by at least one drive at a resonance frequency in one of these modes for purposes of determining a characteristic of the flowing substance.
FIG. 1 depicts a cut-away view of an example vibrating flowmeter 100. For example, vibrating flowmeter 100 may be a Coriolis flowmeter or sensor. Vibrating flowmeter 100 includes four brace bars 102, a case 104, two flow conduits 106, and two manifolds 108. In the embodiment of vibrating flowmeter 100, the two flow conduits 106 each include four bends to form a U-shaped configuration. Manifolds 108 couple flow conduits 106 to the case 104 at the inlet and outlet of the vibrating flowmeter 100. Brace bars 102 couple the flow conduits 106 to one another.
Vibrating flowmeter 100 further includes one or more electronics that transmit a sinusoidal drive signal to a drive (not shown), which is typically a magnet/coil combination with the magnet typically being affixed to the one of the flow conduits 106 and with the coil typically being affixed to a supporting structure or to a second of the flow conduits 106. The drive signal causes the drive to vibrate the flow conduits 106 at a resonance frequency in one of the natural modes of the flow conduits 106. For example, the drive signal may be a periodic electrical current transmitted to the coil.
Vibrating flowmeter 100 may include at least one pick-off (not shown) that detects the motion of a flow conduit and generates a sinusoidal pick-off signal representative of the motion. The pick-off signal is transmitted to the one or more electronics, which, according to well-known principles, determines a characteristic of the flowing substance or adjusts the drive signal, if necessary.
A vibrating flowmeter may include brace bars 102 that connect two flow conduits 106 together. Vibrating flowmeters typically include one or more brace bars towards the inlet or outlet of a meter. In the embodiment of vibrating flowmeter 100, four brace bars 102 are positioned symmetrically on flow conduits 106. Two brace bars 102 are positioned between a manifold 108 and a first bend at each of an inlet and an outlet end of vibrating flowmeter 100. Brace bar 102 allows for separation between a natural frequency of the flow conduits 106, or a frequency at which the flow conduits are typically driven to determine a characteristic of a flowing substance, and modes of vibration found in other components of the meter. Accordingly, by varying the number and position of brace bars 102, the frequency at which the various modes of vibration will be induced in vibrating flowmeter 100 may be somewhat controlled. Furthermore, it may also be desirous to use brace bars 102 to reduce stress on the flow conduits 106 as they oscillate, particularly to reduce stress on the connecting area between a manifold or flange found at the inlet or outlet and the flow conduits 106.
FIG. 2 depicts a top view of brace bar 102. As may be seen from FIG. 2, each brace bar 102 includes two apertures 202 for receiving two flow conduits 106 that may be passed through each of the apertures 202. Brace bar 102 allows two conduits 106 to be connected into a single vibrating structure. However, in order for a brace bar to be effective in this capacity, it is critical that that brace bar maintain a proper alignment.
Vibrating flowmeters are typically built with one of three styles of brace bars. The first type of brace bar is the one-piece brace bar 102 depicted in FIGS. 1 and 2. Brace bar 102 may be used with flow conduit geometries that permit the brace bars to slide over the flow conduits into position. In the example of vibrating flowmeter 100, it may be seen that flow conduits 106 are substantially circular and uniform in cross-section. Flow conduits 106 are also shaped with the same respective bends so that they are positioned substantially equidistant to one another along their respective lengths. The design of brace bar 102 provides for easy manufacturing. The excellent alignment of brace bar 102 also provides for reliable positioning of flow conduits 106. Assembling a vibrating flowmeter with brace bars 102 may present a challenge, however.
The second style of brace bar typically used in vibratory flowmeters is the two-piece brace bar 300 depicted in FIG. 3. Brace bar 300 includes two brace bar sections 302 and 304, with a joint 306 between the brace bar sections. Each brace bar section 302 and 304 includes a respective aperture 202 for a respective flow conduit 106. To assemble brace bar 300, a flow conduit 106 is passed through each of brace bar sections 302 and 304. Brace bar sections 302 and 304 are subsequently joined at joint 306. Brace bar 300 may provide for an easier assembly, but it presents a new problem with regards to alignment.
A third style of brace bar typically used in Coriolis sensors is the three-piece brace bar 400 depicted in FIG. 4. Brace bar 400 includes three sections 402, 404, 406 and two joints 408 and 410. Brace bar 400 may be assembled by inserting a flow conduit 106 into each of sections 402 and 406. Section 404 may then be coupled between sections 402 and 406 via joints 408 and 410. The three-piece design of brace bar 400 may provide for further ease of assembly, but it includes additional joints that may give rise to extra alignment issues.
What is needed is a brace bar that is easy to manufacture, easy to assemble and maintains a proper alignment.